....Did she have to put her hair up at a certain age or not, just wondering?
I can't assure nothing. I knew that girls had their hair up after her 16th birthday in the majority of the cases, but in the case of Sissi, at the time of her engagement she was still 15 years old and her hair is up in all her portraits as well in her first well known photograph. It's possible that she arranged in that way for the portraits.
The only images of her with her hair down are the next:
1 and
2, I saved them from a "time line" of the Empress life, so I think that they mainly come from the imagination of the illustrators
In her other two portraits of childhood -both posing with brother "Gackel"- she has her hair up... so I'm a bit confused :-? But in any case, I find a bit "unusual" that there are three portraits of Sissi after her 16th birthday with her hair down, I read in some thread here that it wasn't considered proper, of course, these weren't official portraits, but I still think that is uncommon -and nice-.
